Solid dihydrocostunolide (VI), on metal-amine reduction furnishes an acid, C15H24O2 (VII; R= H), the constitution of which has been decided from spectral evidence and confirmed by conversion into the known primary alcohol (V) and the hydrocarbon (IV). Conclusive evidence in support of VII (R= H), and the stereochemistry at C4 have been obtained from the ozonolysis of VII (R= CH3) which gives as one of the products, S-(+)-α-methylglutaric ...